Conventional color laser printers produce a generally low gloss, matte finish on printed sheet media. The matte finish is achieved by carefully controlling fusing temperature and fusing time so as to not over fuse the toner to the media. Fusing of toner to generate a matte finish typically leaves air pockets in the toner and a rough surface. The air pockets and rough surface cause light to be scattered when reflected back to the eye, thus presenting a matte finish or appearance. A more glossy finish is generated by further heating or fusing the toner to a point where the surface toner beads are better fused, thus the glossy finish, but the interior toner beads are generally not completely fused.
The process of properly fusing is complicated by factors such as differences in media type and whether or not duplexing is employed in the printer. For example, certain plastic media such as overhead transparencies or other heavy media require a hotter fusing temperature and/or a longer fusing time, compared to normal paper, in order to obtain an image that is sufficiently fused. However, fuser temperature is limited by the range of media supported by the printer. For example, any plastic media supported define a maximum fusing temperature because of their glass point or phase change point which causes warping. On the other hand, any heavy media supported define a minimum fusing temperature that is sufficient to actually fuse the toner to the media. Additionally, when a sheet is duplex imaged, it is a challenge to apply sufficient heat to fuse the second side to a proper appearance without over heating the first side.
When toners fuse completely, there are a minimal number of internal holes that remain to cause light scatter. This results in more light being reflected off of the media back through the toners to the eye. In the case of color toners (i.e., Cyan, Magenta and Yellow), more light means more color. In the case of black toner, less scatter means less light reflected back to the eye for a darker black. Overall, more color and darker blacks mean a more photographic look to images. However, fusing to obtain a photographic like image is also problematic. For example, merely increasing the fusing time or temperature is not always feasible because of the differences in toners, media types, or excess heat that exists during fusing of the second side of a duplex page. Disadvantageously, over fusing can cause media to curl, warp or jam the printer.
Accordingly, an object of the present invention is to provide a tool and method for enabling a photographic finish on sheet media in a matte laser printer.